Ink compositions for thermal ink jet printing

ABSTRACT

Disclosed is an ink composition which comprises water, a dye selected from the group consisting of Direct Blue 199, Direct Yellow 132, Acid Yellow 17, Reactive Red 180, Acid Red 52, and mixtures thereof, and a material of the formula  (F 3  C(F 2  C) n  CH═CHCH 2  OCH(OH)CH 2 ) 2  NCH 2  COO -  ! X +  !, wherein X is a cation and n is an integer of from about 3 to about 20, wherein the ink is substantially free of imidazole. Also disclosed are ink jet printing processes employing the aforementioned ink.

BACKGROUND OF THE INVENTION

The present invention is directed to ink compositions and to processesfor the preparation and use thereof. More specifically, the presentinvention is directed to compositions suitable for use in ink jetprinting processes. One embodiment of the present invention is directedto an ink composition which comprises water, a dye selected from thegroup consisting of Direct Blue 199, Direct Yellow 132, Acid Yellow 17,Reactive Red 180, Acid Red 52, and mixtures thereof, and a material ofthe formula (F₃ C(F₂ C)_(n) CH═CHCH₂ OCH(OH)CH₂)₂ NCH₂ COO⁻ ! X⁺ !,wherein X is a cation and n is an integer of from about 3 to about 20,wherein the ink is substantially free of imidazole.

Ink jet printing systems generally are of two types: continuous streamand drop-on-demand. In continuous stream ink jet systems, ink is emittedin a continuous stream under pressure through at least one orifice ornozzle. The stream is perturbed, causing it to break up into droplets ata fixed distance from the orifice. At the break-up point, the dropletsare charged in accordance with digital data signals and passed throughan electrostatic field which adjusts the trajectory of each droplet inorder to direct it to a gutter for recirculation or a specific locationon a recording medium. In drop-on-demand systems, a droplet is expelledfrom an orifice directly to a position on a recording medium inaccordance with digital data signals. A droplet is not formed orexpelled unless it is to be placed on the recording medium.

Since drop-on-demand systems require no ink recovery, charging, ordeflection, the system is much simpler than the continuous stream type.There are two types of drop-on-demand ink jet systems. One type ofdrop-on-demand system has as its major components an ink filled channelor passageway having a nozzle on one end and a piezoelectric transducernear the other end to produce pressure pulses. The relatively large sizeof the transducer prevents close spacing of the nozzles, and physicallimitations of the transducer result in low ink drop velocity. Low dropvelocity seriously diminishes tolerances for drop velocity variation anddirectionality, thus impacting the system's ability to produce highquality copies. Drop-on-demand systems which use piezoelectric devicesto expel the droplets also suffer the disadvantage of a slow printingspeed.

The other type of drop-on-demand system is known as thermal ink jet, orbubble jet, and produces high velocity droplets and allows very closespacing of nozzles. The major components of this type of drop-on-demandsystem are an ink filled channel having a nozzle on one end and a heatgenerating resistor near the nozzle. Printing signals representingdigital information originate an electric current pulse in a resistivelayer within each ink passageway near the orifice or nozzle, causing theink in the immediate vicinity to evaporate almost instantaneously andcreate a bubble. The ink at the orifice is forced out as a propelleddroplet as the bubble expands. When the hydrodynamic motion of the inkstops, the process is ready to start all over again. With theintroduction of a droplet ejection system based upon thermally generatedbubbles, commonly referred to as the "bubble jet" system, thedrop-on-demand ink jet printers provide simpler, lower cost devices thantheir continuous stream counterparts, and yet have substantially thesame high speed printing capability.

The operating sequence of the bubble jet system begins with a currentpulse through the resistive layer in the ink filled channel, theresistive layer being in close proximity to the orifice or nozzle forthat channel. Heat is transferred from the resistor to the ink. The inkbecomes superheated far above its normal boiling point, and for waterbased ink, finally reaches the critical temperature for bubble formationor nucleation of around 280° C. Once nucleated, the bubble or watervapor thermally isolates the ink from the heater and no further heat canbe applied to the ink. This bubble expands until all the heat stored inthe ink in excess of the normal boiling point diffuses away or is usedto convert liquid to vapor, which removes heat due to heat ofvaporization. The expansion of the bubble forces a droplet of ink out ofthe nozzle, and once the excess heat is removed, the bubble collapses onthe resistor. At this point, the resistor is no longer being heatedbecause the current pulse has passed and, concurrently with the bubblecollapse, the droplet is propelled at a high rate of speed in adirection towards a recording medium. The resistive layer encounters asevere cavitational force by the collapse of the bubble, which tends toerode it. Subsequently, the ink channel refills by capillary action.This entire bubble formation and collapse sequence occurs in about 10microseconds. The channel can be refired after 100 to 500 microsecondsminimum dwell time to enable the channel to be refilled and to enablethe dynamic refilling factors to become somewhat dampened. Thermal inkjet processes are well known and are described in, for example, U.S.Pat. No. 4,601,777, U.S. Pat. No. 4,251,824, U.S. Pat. No. 4,410,899,U.S. Pat. No. 4,412,224, and U.S. Pat. No. 4,532,530, the disclosures ofeach of which are totally incorporated herein by reference.

U.S. Pat. No. 5,019,166 (Schwarz), the disclosure of which is totallyincorporated herein by reference, discloses a thermal ink jet printingcomposition comprising a dye, a liquid medium, and a surfactant selectedfrom the group consisting of polyoxyalkylated ethers, anionic bitailfluorothio alkyls, alkyl aryl sulfonates, alkyl amine quaternary salts,and mixtures thereof. Also disclosed is a process for generating imageswhich comprises causing the ink compositions disclosed herein to beejected from a thermal ink jet printer in imagewise fashion onto asubstrate.

U.S. Pat. No. 5,401,303 (Stoffel et al.), the disclosure of which istotally incorporated herein by reference, discloses a process whereinthe halo effect seen at the interface between a first ink, exhibitingsharp edge acuity, and a second ink, having low surface energy, isaddressed by adding certain fluorocarbon compounds to the first ink.Edge acuity of the first ink is maintained.

U.S. Pat. No. 5,540,765 (Gundlach et al.), the disclosure of which istotally incorporated herein by reference, discloses a thermal ink jetprinting composition which contains a surfactant comprising analkylsulfoxide having an alkyl group of 4 to 6 carbon atoms. Preferably,the composition contains a betaine zwitterionic base anddibutylsulfoxide.

U.S. Pat. No. 5,531,815 (Gundlach et al.), the disclosure of which istotally incorporated herein by reference, discloses a thermal ink jetprinting composition contains a betaine zwitterionic base and aquasisurfactant penetrant.

U.S. Pat. No. 5,389,133 (Gundlach et al.), the disclosure of which istotally incorporated herein by reference, discloses a process forpreparing an aqueous ink composition which comprises adjusting the pH ofthe ink with phosphorous acid or phosphite salts. Also disclosed are inkcompositions prepared by this process. In certain preferred embodiments,the ink compositions can also contain betaine, sulfolone, dimethylsulfoxide, or N,N'-bis(3-aminopropyl)-1,2-ethylenediamine, as well asmixtures thereof. In other preferred embodiments, the ink compositioncomprises an organic component selected from the group consisting ofsulfolane, dimethyl sulfoxide, and mixtures thereof, and anions selectedfrom the group consisting of phosphite, hypophosphite, phosphate,polyphosphate, sulfate, hexafluorophosphate, glycolate, acetate,ethylenediaminetetroacetate, formate, borate, sulfite, sulfamate, andmixtures thereof.

Copending application U.S. Ser. No. 08/961,335, filed concurrentlyherewith, entitled "Improved Ink Compositions for Thermal Ink JetPrinting," with the named inventors Kurt B. Gundlach, Richard L. Colt,and Edward J. Radigan, Jr., the disclosure of which is totallyincorporated herein by reference, discloses an ink composition whichcomprises water, a colorant, betaine, a tertiary amine, and a materialof the formula (F_(2n+1) C_(n) CH₂ S)₂ (CH₃)C--CH₂ CH₂ COO⁻ ! B⁺ !,wherein n is an integer of from about 8 to about 20 and B is a cation.In one specific embodiment, n is 10 and B is (HO--CH₂ CH₂)₂ NH₃ +. Inanother specific embodiment, the tertiary amine is 1-methylimidazole. Inyet another specific embodiment of the present invention, the colorantis an anionic dye with carboxylate groups, sulfonate groups, or bothcarboxylate and sulfonate groups. Also disclosed is a process forpreparing the aforementioned ink composition wherein a liquid containingthe material of the formula (F_(2n+1) C_(n) CH₂ S)₂ (CH₃)C--CH₂ CH₂ COO⁻! B⁺ ! is subjected to centrifugation. Also disclosed are ink jetprinting processes employing the aforementioned ink.

Copending application U.S. Ser. No. 08/961,435, filed concurrentlyherewith, entitled "Improved Ink Compositions for Thermal Ink JetPrinting," with the named inventors Kurt B. Gundlach, Luis A. Sanchez,Cheryl A. Hanzlik, Kathy-Jo Brodsky, Richard L. Colt, Aileen M. Montes,and Edward J. Radigan, Jr., the disclosure of which is totallyincorporated herein by reference, discloses an ink composition whichcomprises (a) water, (b) a colorant, (c) a fluorinated material selectedfrom: (1) those of the formula (F_(2n+1) C_(n) CH₂ S)₂ (CH₃)C--CH₂ CH₂COO⁻ ! B⁺ !, wherein n is an integer of from about 8 to about 20 and Bis a cation, (2) those of the formula (F₃ C(F₂ C)_(n) CH═CHCH₂OCH(OH)CH₂)₂ NCH₂ COO⁻ ! X⁺ !, wherein X is a cation and n is an integerof from about 3 to about 20, and (3) mixtures thereof, and (d) amonomeric compound having at least two carboxylic acid functionalgroups. Also disclosed is a process for preparing said ink compositionwhich comprises (i) admixing the ink ingredients, and (ii) subjectingthe mixture thus formed to ultrasonification, thereby reducing theaverage particle diameter of liposomes of the fluorinated material inthe ink. Further disclosed is a process which entails (i) incorporatinginto an ink jet printing apparatus the aforementioned ink composition,and (ii) causing droplets of the ink composition to be ejected in animagewise pattern onto a substrate. In a preferred embodiment, theprinting apparatus employs a thermal ink jet process wherein the ink inthe nozzles is selectively heated in an imagewise pattern, therebycausing droplets of the ink to be ejected in imagewise pattern.

Copending application U.S. Ser. No. 08/961,118, filed concurrentlyherewith, entitled "Improved Ink Compositions for Thermal Ink JetPrinting," with the named inventors Kurt B. Gundlach, Luis A. Sanchez,Cheryl A. Hanzlik, Kathy-Jo Brodsky, Richard L. Colt, Aileen M. Montes,Danielle Avolio, and Rachael L. McGrath, the disclosure of which istotally incorporated herein by reference, discloses an ink compositionwhich comprises (a) water, (b) a colorant, and (c) a material of theformula (F₃ C(F₂ C)_(n) CH═CHCH₂ OCH(OH)CH₂)₂ NCH₂ COO⁻ ! X⁺ !, whereinX is a cation and n is an integer of from about 3 to about 20. Alsodisclosed are processes for preparing the ink composition and ink jetprinting processes with the ink composition.

Copending application U.S. Ser. No. 08/961,461, filed concurrentlyherewith, entitled "Improved Ink Compositions for Thermal Ink JetPrinting," with the named inventors Kurt B. Gundlach and Walter F.Wafler, the disclosure of which is totally incorporated herein byreference, discloses an ink composition which comprises water, acolorant, a nonionic surfactant, and a fluorinated material selectedfrom the group consisting of (a) those of the formula (F_(2n+1) C_(n)CH₂ S)₂ (CH₃)C--CH₂ CH₂ COO⁻ ! B⁺ !, wherein n is an integer of fromabout 8 to about 20 and B is a cation, and (b) those of the formula (F₃C(F₂ C)_(n) CH═CHCH₂ OCH(OH)CH₂)₂ NCH₂ COO⁻ ! X⁺ !, wherein X is acation. Also disclosed are ink jet printing processes employing theaforementioned ink.

Copending application U.S. Ser. No. 08/961,637, filed concurrentlyherewith, entitled "Improved Ink Compositions for Thermal Ink JetPrinting," with the named inventors Kurt B. Gundlach, Luis A. Sanchez,Cheryl A. Hanzlik, Kathy-Jo Brodsky, Richard L. Colt, and Aileen M.Montes, the disclosure of which is totally incorporated herein byreference, discloses an ink composition which comprises water, ananionic dye having at least one anionic functional group and having acationic counterion associated with each anionic functional group, and amaterial of the formula (F_(2n+1) C_(n) CH₂ S)₂ (CH₃)C--CH₂ CH₂ COO⁻ !B⁺ !, wherein n is an integer of from about 8 to about 20 and B is acation, said ink composition containing alkali metal cations in anamount of no more than about 1×10⁻³ moles per liter. Also disclosed areink jet printing processes employing the aforementioned ink.

Copending application U.S. Ser. No. 08/961,173, filed concurrentlyherewith, entitled "Improved Ink Compositions for Thermal Ink JetPrinting," with the named inventors Kurt B. Gundlach, Luis A. Sanchez,Richard L. Colt, and Rachael L. McGrath, the disclosure of which istotally incorporated herein by reference, discloses an ink compositionwhich comprises water, a colorant, a bisquaternary ammonium compound,and a material of the formula (F₃ C(F₂ C)_(n) CH═CHCH₂ OCH(OH)CH₂)₂ NCH₂COO⁻ ! X⁺ !, wherein X is a cation and n is an integer of from about 3to about 20. Also disclosed are ink jet printing processes employing theaforementioned ink.

Copending application U.S. Ser. No. 08/961,393, filed concurrentlyherewith, entitled "Improved Ink Compositions for Thermal Ink JetPrinting," with the named inventors Kurt B. Gundlach, Richard L. Colt,Luis A. Sanchez, and Danielle Avolio, the disclosure of which is totallyincorporated herein by reference, discloses an ink composition whichcomprises water, a colorant, 1,4-diazabicyclo(2.2.2)octane, and afluorinated material selected from the group consisting of (a) those ofthe formula (F_(2n+1) C_(n) CH₂ S)₂ (CH₃)C--CH₂ CH₂ COO⁻ ! B⁺ !, whereinn is an integer of from about 8 to about 20 and B is a cation, and (b)those of the formula (F₃ C(F₂ C)_(n) CH═CHCH₂ OCH(OH)CH₂)₂ NCH₂ COO⁻ !X⁺ !, wherein X is a cation and n is an integer of from about 3 to about20. Also disclosed are processes for preparing the aforementioned inkand ink jet printing processes employing the aforementioned ink.

Copending application U.S. Ser. No. 08/960,792, filed concurrentlyherewith, entitled "Improved Ink Compositions for Thermal Ink JetPrinting," with the named inventors Kurt B. Gundlach, Luis A. Sanchez,Richard L. Colt, and Danielle Avolio, the disclosure of which is totallyincorporated herein by reference, discloses an ink composition whichcomprises (a) water, (b) a colorant selected from the group consistingof Acid Yellow 23, Acid Yellow 17, Reactive Red 180, Direct Blue 199,Acid Blue 9, and mixtures thereof, (c) imidazole, (d) an additiveselected from the group consisting of betaine, polyethylene oxide, andmixtures thereof, and (e) a material of the formula (F₃ C(F₂ C)_(n)CH═CHCH₂ OCH(OH)CH₂)₂ NCH₂ COO⁻ ! X⁺ !, wherein X is a cation and n isan integer of from about 3 to about 20. Also disclosed are ink jetprinting processes employing the aforementioned ink.

Copending application U.S. Ser. No. 08/961,334, filed concurrentlyherewith, entitled "Improved Ink Compositions for Thermal Ink JetPrinting," with the named inventors Kurt B. Gundlach, Luis A. Sanchez,Danielle Avolio, Maura A. Sweeney, and Richard L. Colt, the disclosureof which is totally incorporated herein by reference, discloses an inkcomposition which comprises (1) water, (2) a colorant, (3) a material ofthe formula (F₃ C(F₂ C)_(n) CH═CHCH₂ OCH(OH)CH₂)₂ NCH₂ COO⁻ ! X⁺ !,wherein X is a cation and n is an integer of from about 3 to about 20,(4) a polymer selected from the group consisting of (a) tetrafunctionalblock copolymers derived from the addition of propylene oxide andethylene oxide to ethylenediamine; (b) polyethylene oxide-polypropyleneoxide-polyethylene oxide triblock copolymers; (c) polypropyleneoxide-polyethylene oxide-polypropylene oxide triblock copolymers; (d)ethoxylated 2-naphthol polymers; and (e) mixtures thereof; and (5) anadditive selected from the group consisting of (i) diethylene glycol;(ii) glycerol; (iii) trimethylol propane; (iv) urea; (v) n-methylpyrrolidone; (vi) sulfolane; (vii) 1,4 diazabicyclo(2.2.2)octane; (viii)cyclohexylpyrrolidone; and (ix) mixtures thereof. Also disclosed are inkjet printing processes employing the aforementioned ink.

While known compositions and processes are suitable for their intendedpurposes, a need remains for ink compositions with improvedcharacteristics. In addition, a need remains for ink compositions whichexhibit reduced or no intercolor bleed when printed adjacent to otherinks of different colors. Further, a need remains for ink compositionswhich exhibit good shelf stability. Additionally, a need remains for inkcompositions having improved colorimetry. There is also a need for inkcompositions which exhibit reduced intercolor bleed in combination withimproved shelf stability and improved colorimetry. In addition, there isa need for ink compositions with good lightfastness characteristics.Further, there is a need for ink compositions which exhibit goodwaterfastness characteristics. Additionally, there is a need for inkcompositions which enable the generation of prints with excellentoptical density. A need also remains for ink compositions having dyecolorants which exhibit reduced intercolor bleed with ink compositionshaving pigment colorants, whether or not the pigmented ink compositionscontain a fluorinated material. In addition, a need remains for inkcompositions with improved color gamut. Further, a need remains for inkcompositions which exhibit reduced showthrough when printed on papersubstrates. Additionally, a need remains for ink compositions suitablefor printing onto a wide variety of substrates. There is also a need forink compositions which are relatively benign with respect to anytendency to cause degradation of common thermal ink jet printheadmaterials. In addition, there is a need for ink compositions whichenable the generation of prints on various papers with reduced oreliminated curling of the paper.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide ink compositionswith the above noted advantages.

It is another object of the present invention to provide inkcompositions with improved characteristics.

It is yet another object of the present invention to provide inkcompositions which exhibit reduced or no intercolor bleed when printedadjacent to other inks of different colors.

It is still another object of the present invention to provide inkcompositions which exhibit good shelf stability.

Another object of the present invention is to provide ink compositionshaving improved colorimetry.

Yet another object of the present invention is to provide inkcompositions which exhibit reduced intercolor bleed in combination withimproved shelf stability and improved colorimetry.

Still another object of the present invention is to provide inkcompositions with good lighffastness characteristics.

It is another object of the present invention to provide inkcompositions which exhibit good waterfastness characteristics.

It is yet another object of the present invention to provide inkcompositions which enable the generation of prints with excellentoptical density.

Another object of the present invention is to provide ink compositionshaving dye colorants which exhibit reduced intercolor bleed with inkcompositions having pigment colorants, whether or not the pigmented inkcompositions contain a fluorinated material.

Yet another object of the present invention is to provide inkcompositions with improved color gamut.

Still another object of the present invention is to provide inkcompositions which exhibit reduced showthrough when printed on papersubstrates.

It is another object of the present invention to provide inkcompositions suitable for printing onto a wide variety of substrates.

It is yet another object of the present invention to provide inkcompositions which are relatively benign with respect to any tendency tocause degradation of common thermal ink jet printhead materials.

It is still another object of the present invention to provide inkcompositions which enable the generation of prints on various paperswith reduced or eliminated curling of the paper.

These and other objects of the present invention (or specificembodiments thereof) can be achieved by providing an ink compositionwhich comprises water, a dye selected from the group consisting ofDirect Blue 199, Direct Yellow 132, Acid Yellow 17, Reactive Red 180,Acid Red 52, and mixtures thereof, and a material of the formula (F₃C(F₂ C)_(n) CH═CHCH₂ OCH(OH)CH₂)₂ NCH₂ COO⁻ ! X⁺ !, wherein X is acation and n is an integer of from about 3 to about 20, wherein the inkis substantially free of imidazole.

DETAILED DESCRIPTION OF THE INVENTION

Inks of the present invention contain an aqueous liquid vehicle, a dyeselected from the group consisting of Direct Blue 199, Direct Yellow132, Acid Yellow 17, Reactive Red 180, Acid Red 52, and mixturesthereof, and a material of the formula (F₃ C(F₂ C)_(n) CH═CHCH₂OCH(OH)CH₂)₂ NCH₂ COO⁻ ! X⁺ !, wherein X is a cation and n is an integerof from about 3 to about 20, wherein the ink is substantially free ofimidazole. The liquid vehicle can consist solely of water, or it cancomprise a mixture of water and a water soluble or water miscibleorganic component, such as ethylene glycol, propylene glycol, diethyleneglycols, glycerine, dipropylene glycols, polyethylene glycols,polypropylene glycols, tripropylene glycol monomethyl ether, amides,ethers, urea, substituted ureas, ethers, carboxylic acids and theirsalts, esters, alcohols, organosulfides, organosulfoxides, sulfones(such as sulfolane), alcohol derivatives, carbitol, butyl carbitol,cellusolve, ether derivatives, amino alcohols, ketones,N-methylpyrrolidinone, 2-pyrrolidinone, cyclohexylpyrrolidone,hydroxyethers, amides, sulfoxides, lactones, polyelectrolytes, methylsulfonylethanol, imidazole, and other water soluble or water misciblematerials, as well as mixtures thereof. When mixtures of water and watersoluble or miscible organic liquids are selected as the liquid vehicle,the water to organic ratio typically ranges from about 100:0 to about30:70, and preferably from about 97:3 to about 40:60. The non-watercomponent of the liquid vehicle generally serves as a humectant whichhas a boiling point higher than that of water (100° C.). In the inkcompositions of the present invention, the liquid vehicle is typicallypresent in an amount of from about 60 to about 95 percent by weight ofthe ink, and preferably from about 70 to about 90 percent by weight ofthe ink, although the amount can be outside these ranges.

In one specific embodiment, the liquid vehicle contains a penetrantmaterial selected from betaine, cyclohexyl pyrrolidinone, butyl carbitol(diethylene glycol monobutyl ether), tripropylene glycol monomethylether, or mixtures thereof. The penetrant material is present in anyeffective or desired amount, typically from about 0.1 to about 20percent by weight, and preferably from about 3 to about 15 percent byweight, although the amount can be outside these ranges. Inks of thisspecific embodiment are preferred over those containing a surfactantbecause of frequently reduced viscosity.

Also contained in the ink is a material of the formula ##STR1## whereinX+ is a cation and n is an integer of from about 3 to about 20,preferably from about 4 to about 15, and more preferably from about 5 toabout 11. Examples of suitable cations include (HO--CH₂ CH₂)₂ NH₂ +,(HO--CH₂ CH₂)₃ NH+, an imidazolium cation such as imidozolium, N-methylimidazolium, or N-butyl imidazolium, tris(hydroxymethyl)aminomethanehydrochloride, tris(hydroxymethyl)aminomethane hydrocitrate, protonated1,4-diazabicyclo(2.2.2)octane, and the like. Materials of this formulaare available from, for example, Ciba-Geigy, Ardsley, New York(Greensboro, N.C.) as LODYNE P-502, containing a mixture of compoundswherein n has varying values and has an average value of about 9. Thematerial of this formula is present in the ink in any effective ordesired amount; typically, the amount ranges from about 0.1 to about 10percent by weight of the ink, preferably from about 0.25 to about 6percent by weight of the ink, more preferably from about 0.5 to about 5percent by weight of the ink, and even more preferably from about 1 toabout 4 percent by weight of the ink, although the amount can be outsidethese ranges.

In one preferred embodiment of the present invention, the fluorinatedmaterial is of the formula ##STR2## wherein n is 5. This material isavailable from, for example, Ciba-Geigy, Ardsley, New York (Greensboro,N.C.) as LODYNE P-502L, containing the fluorocarbon whereinsubstantially all of the material has exactly 6 carbon atoms in each ofthe fluorinated hydrocarbon chains. Inks containing this materialexhibit improved shelf stability, even when the fluorocarbon and/or theink are not subjected to ultrasonification or high shear mixing. Thesematerials also exhibit good shelf stability with a wide variety of dyes,whereas inks containing mixtures of fluorocarbons of the above formulawherein n has varying values may be compatible with some dyes and mayexhibit reduced shelf stability with other dyes. The ink fabricationprocess is accordingly simplified, with no need for procedures otherthan simple mixing of the ingredients to obtain optimal performance.

Also contained in the ink composition of the present invention is a dye.The dye is selected from the group consisting of Direct Blue 199(commercially available as, for example, PROJET CYAN 1 from ZenecaColors, Dighton, Mass.), Direct Yellow 132 (commercially available as,for example, PROJET YELLOW 1G from Zeneca Colors, Dighton, Mass.), AcidYellow 17 (commercially available from, for example Tricon Colors,Elmwood Park, N.J.), Reactive Red 180 (commercially available as, forexample, PROJET MAGENTA 1T from Zeneca Colors, Dighton, Mass.), Acid Red52 (commercially available from, for example Tricon Colors, ElmwoodPark, N.J.), and mixtures thereof. The dye is present in the inkcomposition in any effective amount, typically from about 0.5 to about15 percent by weight of the ink, preferably from about 0.5 to about 8percent by weight of the ink, more preferably from about 1 to about 10percent by weight of the ink, and even more preferably from about 1 toabout 6 percent by weight of the ink, although the amount can be outsideof these ranges.

Inks of the present invention containing the fluorinated material andone or more of the above dye compositions exhibit excellent shelfstability as a result of the compatibility of these dyes with thefluorinated material. In addition, the inks exhibit good compatibilitywith printhead hardware, improved waterfastness and lightfastness,excellent optical density, and good color quality.

Optionally, 1,4-diazabicyclo(2.2.2)octane is also contained in the ink.This material is of the formula ##STR3## The1,4-diazabicyclo(2.2.2)octane acts as a buffer in the ink composition,maintaining the ink containing the fluorinated material additive at adesirable pH in the event of acid contamination. In addition, the1,4-diazabicyclo(2.2.2)octane is highly efficient as a buffer, withrelatively small amounts being required in the ink to enable thebuffering function. Typically, the 1,4-diazabicyclo(2.2.2)octane ispresent in an amount from about 0.1 to about 6 percent by weight of theink, preferably from about 0.5 to about 4 percent by weight of the ink,and more preferably from about 1 to about 3 percent by weight of theink, although the amount can be outside these ranges. Further, thepresence of the 1,4-diazabicyclo(2.2.2)octane enables buffered inkcompositions containing the fluorinated material without undesirableincrease in viscosity, particularly when the ink is heated or subjectedto changes in pH.

Optionally, ink compositions contain a bisquaternary ammonium compound.Bisquaternary ammonium compounds suitable for the present inventioninclude (but are not limited to) those of the general formula ##STR4##wherein each of R₁, R₂, R₃, R₄, R₅, and R₆, independently of the others,is an alkyl group, preferably with from 1 to about 6 carbon atoms (andwherein the alkyl group can be substituted with, for example, hydroxidegroups, halide groups, or the like, R₇ is an alkylene group, preferablywith from about 2 to about 10 carbon atoms (and wherein the alkylenegroup can be substituted with, for example, hydroxide groups, halidegroups, or the like), and wherein A is an anion. Examples of suitableanions include (but are not limited to) hydroxide, halide, citrate,ethylene diamine tetraacetate, phosphite, and the like. Examples ofsuitable bisquaternary ammonium compounds include N,N'-hexamethylenebis(tributyl ammonium) compounds, N,N'-hexamethylenebis(trimethyl ammonium) compounds, and the like.Specific examples of suitable bisquaternary ammonium compounds includeN,N'-hexamethylenebis(tributyl ammonium hydroxide), of the formula##STR5## N,N'-hexamethylenebis(trimethyl ammonium bromide) (also calledhexamethonium bromide), of the formula ##STR6## and the like. Thebisquaternary ammonium compound is present in the ink in any desired oreffective amount, typically in a stoichiometric amount of from about 0.1to about 4 moles of bisquaternary ammonium compound per one mole offluorinated material, preferably in a stoichiometric amount of fromabout 0.25 to about 2 moles of bisquaternary ammonium compound per onemole of fluorinated material, and more preferably in a stoichiometricamount of from about 0.5 to about 1 moles of bisquaternary ammoniumcompound per one mole of fluorinated material, although the relativeamounts can be outside these ranges. The bisquaternary ammonium compoundtypically is present in the ink in an amount of from about 0.1 to about10 percent by weight of the ink, and preferably from about 0.5 to about4 percent by weight of the ink, although the amount can be outside theseranges.

While not being limited to any particular theory, it is believed thatthe bisquaternary ammonium compound becomes associated with thefluorinated material (which has a carboxylic acid substituent) andimparts shelf stability to the ink. It is further hypothesized that thebisquaternary ammonium compound associated with the fluorinated materialmay reduce liposome lattice energy through ionic complexation, therebyarresting liposome growth and inhibiting phase separation in the inkcomposition. Additionally, it is hypothesized that the bisquaternaryammonium compound associated with the fluorinated material may increasethe liposome radius of curvature, thereby stabilizing small liposomesrelative to large liposomes (which may undesirably increase inkviscosity).

Optionally, betaine can also be present in the inks of the presentinvention. Betaine is commercially available from, for example,Finnsugar Biomedical, Helsinki, Finland. Betaine is present in the inkin any effective or desired amount; typically, the amount ranges fromabout 5 to about 25 percent by weight of the ink, and preferably fromabout 10 to about 20 percent by weight of the ink, although the amountcan be outside these ranges. In one embodiment of the present invention,betaine is present in the ink compositions in combination withdipropylene glycol. In this embodiment, the dipropylene glycol typicallyis present in the ink in an amount of up to about 20 percent by weightof the ink, preferably from about 5 to about 15 percent by weight of theink, and more preferably from about 5 to about 10 percent by weight ofthe ink, although the amount can be outside these ranges. In anotherpreferred embodiment of the present invention, betaine is present in theink compositions in combination with butyl carbitol. In this embodiment,the butyl carbitol typically is present in the ink in an amount of up toabout 15 percent by weight of the ink, preferably from about 2 to about10 percent by weight of the ink, and more preferably from about 2 toabout 5 percent by weight, although the amount can be outside theseranges.

Optionally, a monomeric compound having at least two carboxylic acidfunctional groups is also contained in the inks of the presentinvention. Examples of suitable multifunctional acids includeethylenediamine tetraacetic acid, aspartic acid, citric acid, malicacid, glutaric acid, adipic acid, oxalic acid, malonic acid, maleicacid, alpha keto glutaric acid, and the like. The multifunctional acidis present in the ink in any effective or desired amount, typically fromabout 0.05 to about 5 percent by weight of the ink, preferably fromabout 0.2 to about 3 percent by weight of the ink, and more preferablyfrom about 1 to about 2 percent by weight of the ink, although theamount can be outside these ranges. Additional examples ofmultifunctional acids include those disclosed in columns 19 to 22 ofU.S. Pat. No. 5,589,277, the disclosure of which is totally incorporatedherein by reference. While not being limited to any particular theory,it is believed that the presence of the multifunctional acid incombination with the fluorocarbon material enhances the shelf stabilityof the inks of the present invention. The fluorocarbon material in anink in the absence of a multifunctional acid may exhibit a tendency tosalt out of the ink, particularly when the colorant is an anionic dye.It is believed that hydrogen bonding occurs between the polar carboxylgroups of the fluorocarbon material and the carboxyl groups of themultifunctional acid, thereby stabilizing the liposome structure of thefluorocarbon material in the ink. The stabilized ink also exhibitsimproved jetting characteristics and improved viscosity stability withrespect to pH and temperature. It is believed that the stabilizedliposome structure renders the liposomes resistant to coalescence,thereby improving resistance to viscosity build.

The ink compositions of the present invention contain substantially noimidazole. Imidazole can be used in ink compositions containingfluorinated materials such as those contained in the inks of the presentinvention to enhance the shelf stability of the ink. Since imidazole cancause degradation of many materials commonly used to fabricate thermalink jet printheads, however, inks of the present invention areparticularly benign with respect to ink jet printhead materials.

In another preferred embodiment, the ink compositions of the presentinvention contain tripropylene glycol monomethyl ether. When present,the tripropylene glycol monomethyl ether is present in any desired oreffective amount, typically up to about 15 percent by weight of the ink,and preferably up to about 10 percent by weight of the ink, although theamount can be outside these ranges. This material is believed tofunction as a penetrant and also imparts shelf stability to the ink.

Other additives can also be present in the inks. For example, one ormore surfactants or wetting agents can be added to the ink. Theseadditives may be of the cationic, anionic, or nonionic types. Suitablesurfactants and wetting agents include sodium lauryl sulfate, TAMOL® SN,TAMOL® LG, those of the TRITON® series available from Rohm and HaasCompany, those of the MARASPERSE® series, those of the IGEPAL® seriesavailable from GAF Company, those of the TERGITOL® series, SURFYNOL® GAavailable from Air Products and Chemicals Co., and other commerciallyavailable surfactants. These surfactants and wetting agents are presentin effective amounts, generally from 0 to about 10 percent by weight,and preferably from about 0.01 to about 4 percent by weight, althoughthe amount can be outside of this range.

In one specific embodiment the ink contains a nonionic surfactant. Anysuitable or desired nonionic surfactant may be employed. Examples ofsuitable nonionic surfactants include octylphenoxy polyethoxy ethanols,such as TRITON X-100, available from Union Carbide Co., Danbury, Conn.,acetylenic diols such as 2,4,7,9-tetramethyl-5-decyn-4,7-diol and thelike, such as SURFYNOL GA and SURFYNOL CT-136, available from AirProducts & Chemicals Co., Allentown, Pa., trimethylnonylpolyethylene-glycol ethers, such as TERGITOL TMN-10 (containing 10oxyethylene units, believed to be of the formula C₁₂ H₂₅ O(C₂ H₄ O)₅ H),available from Union Carbide Co., Danbury, Conn., non-ionic esters ofethylene oxide, such as MERPOL SH (believed to be of the formula CH₃(CH₂)₁₂ (OC₂ H₄)₈ OH), available from E. I. Du Pont de Nemours & Co.,Wilmington, Del., non-ionic esters of ethylene oxide and propyleneoxide, such as MERPOL LFH (believed to be of the formula CH₃ (CH₂),(OC₂H₄)₈ (OC₃ H₆)₈ OH where n is an integer from about 12 to about 16),available from E. I. Du Pont de Nemours & Co., Wilmington, Del., and thelike, as well as mixtures thereof. The nonionic surfactant is present inthe ink in any suitable or desired amount, typically from about 0.1 toabout 5 percent by weight of the ink, and preferably from about 0.5 toabout 2 percent by weight of the ink, although the amount can be outsideof these ranges.

Polymeric additives can also be added to the inks to enhance theviscosity and the stability of the ink. Water soluble polymers such asGum Arabic, polyacrylate salts, polymethacrylate salts, polyvinylalcohols, hydroxy propylcellulose, hydroxyethylcellulose,polyvinylpyrrolidinone, polyvinylether, starch, polysaccharides,polyethylene oxide, block copolymers of polyethylene oxide andpolypropylene oxide, polyvinylpyridine, polyethyleneimine,polyhydroxyethyl ethyleneimine, polyquaternary salts, and the like aretypical polymeric additives. Polymeric additives can be present in theink of the present invention in amounts of from 0 to about 10 percent byweight, and preferably from about 0.01 to about 5 percent by weight,although the amount can be outside this range.

One example of an additive to the inks is a polymeric additiveconsisting of two polyalkylene oxide chains bound to a centralbisphenol-A-type moiety. This additive is of the formula ##STR7##wherein R¹ and R² are independently selected from the group consistingof hydrogen, alkyl groups with from 1 to about 8 carbon atoms, such asmethyl, ethyl, propyl, and the like, and alkoxy groups with from 1 toabout 8 carbon atoms, such as methoxy, ethoxy, butoxy, and the like, R³and R⁴ are independently selected from the group consisting of alkylgroups with from 1 to about 4 carbon atoms, and x and y are eachindependently a number of from about 100 to about 400, and preferablyfrom about 100 to about 200. Generally, the molecular weight of thepolyalkylene oxide polymer is from about 14,000 to about 22,000, andpreferably from about 15,000 to about 20,000, although the molecularweight can be outside this range. Materials of this formula arecommercially available; for example, Carbowax M20, a polyethyleneoxide/bisphenol-A polymer of the above formula with a molecular weightof about 18,000, available from Union Carbide Corporation, Danbury,Conn., is a suitable polymeric additive for the inks of the presentinvention. In addition, compounds of the above formula can be preparedby the methods disclosed in Polyethers, N. G. Gaylord, John Wiley &Sons, N.Y. (1963) and "Laboratory Synthesis of Polyethylene GlycolDerivatives," J. M. Harris, J. Molecular Science--Rev. Macromol. Chem.Phys., C25(3), 325-373 (1985), the disclosures of each of which aretotally incorporated herein by reference. The polyalkylene oxideadditive is generally present in the ink in an amount of at least about1 part per million. Typically, the polyalkylene oxide additive ispresent in amounts of up to 1 percent by weight of the ink, andpreferably in amounts of up to 0.5 percent by weight of the ink; largeramounts of the additive may increase the viscosity of the ink beyond thedesired level, but larger amounts can be used in applications whereinincreased ink viscosity is not a problem. Inks containing theseadditives are disclosed in U.S. Pat. No. 5,207,825, the disclosure ofwhich is totally incorporated herein by reference.

Optionally, ink compositions of the present invention can also contain apolyethylene oxide-polypropylene oxide block copolymer. Suitablepolymers include tetrafunctional block copolymers derived from thesequential addition of propylene oxide and ethylene oxide toethylenediamine, such as those of the general formula ##STR8## whereinx, x', x", x'", y, y', y", and y'" are each integers representing thenumber of repeating monomer units and have values such that themolecular weight range of the compound is from about 1,650 to about27,000, the values of x, x', x", and x'" are each such that thepolypropylene oxide segments of the compound have a total molecularweight of at least about 250 and preferably from about 500 to about7,000, and the values of y, y', y", and y'" are each such that thepolyethylene oxide segments constitute from about 5 to about 90 percentby weight of the total molecular weight of the compound, and preferablyfrom about 10 to about 80 percent by weight of the total molecularweight of the compound, with typical values for x, x', x", and x'" beingfrom 1 to about 127 and typical values for y, y', y", and y'" being from1 to about 110, such as TETRONIC 904, wherein the values of x, x', x",x'", y, y', y", and y'" are each such that the total molecular weight ofthe polypropylene oxide blocks of the compound is from about 3,900 toabout 4,500 and the ethylene oxide segments make up about 40 percent byweight of the compound (average number of propylene oxide groups permolecule from about 68 to about 76 (typically from about 17 to about 19repeating units per chain, with four chains per molecule), totalmolecular weight from about 6,500 to about 7,500), TETRONIC 704, whereinthe values of x, x', x", x'", y, y', y", and y'" are each such that thetotal molecular weight of the polypropylene oxide blocks of the compoundis from about 2,500 to about 3,600 and the ethylene oxide segments makeup about 40 percent by weight of the compound (average number ofpropylene oxide groups per molecule from about 43 to about 62 (typicallyfrom about 13 to about 15 repeating units per chain, with four chainsper molecule), total molecular weight from about 4,150 to about 6,000),and TETRONIC 304, wherein the values of x, x', x", x'", y, y', y", andy'" are each such that the total molecular weight of the polypropyleneoxide blocks of the compound is from about 500 to about 1,900 and theethylene oxide segments make up about 40 percent by weight of thecompound (average number of propylene oxide groups per molecule fromabout 8 to about 32 (typically from about 2 to about 8 repeating unitsper chain, with four chains per molecule), total molecular weight fromabout 800 to about 3,200), all commercially available from BASF,Parsippany, N.J. Also suitable are polyethylene oxide-polypropyleneoxide-polyethylene oxide triblock copolymers, including those formed bythe controlled addition of propylene oxide to the two hydroxyl groups ofpropylene glycol, followed by addition of ethylene oxide, such as thoseof the general formula ##STR9## wherein x, x', and y are each integersrepresenting the number of repeating monomer units and have values suchthat the molecular weight range of the compound is from about 1,000 toabout 14,000, the value of y is such that the polypropylene oxidesegment of the compound has a molecular weight of at least about 900 andpreferably is from about 950 to about 4,000, and the values of x and x'are such that the polyethylene oxide segments constitute from about 5 toabout 90 percent by weight of the total molecular weight of thecompound, and preferably from about 10 to about 80 percent by weight ofthe total molecular weight of the compound, such as PLURONIC L35,wherein the values of x, x', and y are each such that the molecularweight of the polypropylene oxide block of the compound is from about925 to about 1,050 and the ethylene oxide segments make up about 50percent by weight of the compound (average number of propylene oxidegroups per molecule from about 16 to about 18, total molecular weightfrom about 1,900 to about 2,000), PLURONIC L64, wherein the values of x,x', and y are each such that the molecular weight of the polypropyleneoxide block of the compound is from about 1,625 to about 1,875 and theethylene oxide segments make up about 40 percent by weight of thecompound (average number of propylene oxide groups per molecule fromabout 28 to about 32, total molecular weight from about 2,700 to about3,150); PLURONIC L62F, which is a mixture containing about 90 percent byweight of a compound wherein the values of x, x', and y are each suchthat the molecular weight of the polypropylene oxide block of themolecule is from about 1,625 to about 1,875 and the ethylene oxidesegments make up about 20 percent by weight of the molecule (averagenumber of propylene oxide groups per molecule from about 28 to about 32,total molecular weight from about 2,000 to about 2,350) and about 10percent by weight of a compound wherein the values of x, x', and y areeach such that the molecular weight of the polypropylene oxide block ofthe molecule is 1,625 to about 1,875 and the ethylene oxide segmentsmake up about 10 percent by weight of the molecule (average number ofpropylene oxide groups per molecule from about 28 to about 32, totalmolecular weight from about 1,800 to about 2,100); and PLURONIC P65,wherein the values of x, x', and y are each such that the molecularweight of the polypropylene oxide block of the molecule is from about1,625 to about 1,875 and the ethylene oxide segments make up about 50percent by weight of the molecule (average number of propylene oxidegroups per molecule from about 28 to about 32, total molecular weightfrom about 3,250 to about 3,750), all commercially available from BASF.Also suitable are polypropylene oxide-polyethylene oxide-polypropyleneoxide triblock copolymers, including those formed by the addition ofethylene oxide to ethylene glycol, followed by addition of propyleneoxide, such as those of the general formula ##STR10## wherein x, x', andy are each integers representing the number of repeating monomer unitsand have values such that the molecular weight range of the compound isfrom about 1,000 to about 14,000, the value of x and x' are such thatthe polypropylene oxide segments of the compound have a molecular weightof at least about 900 and preferably from about 1000 to about 3,100, andthe value of y is such that the polyethylene oxide segment constitutesfrom about 5 to about 90 percent by weight of the total molecular weightof the compound, and preferably from about 10 to about 80 percent byweight of the total molecular weight of the compound, such as PLURONIC10R-5, wherein the values of x, x', and y are each such that themolecular weight of the polypropylene oxide blocks of the compound isabout 1,000 and the ethylene oxide segments make up about 50 percent byweight of the compound, commercially available from BASF. Furtherinformation regarding the synthesis and structure of the TETRONICS andPLURONICS materials is disclosed in, for example, U.S. Pat. No.4,062,907, U.S. Pat. No. 5,114,755, U.S. Pat. No. 5,001,165, U.S. Pat.No. 4,536,254, U.S. Pat. No. 4,670,058, U.S. Pat. No. 4,578,150, U.S.Pat. No. 5,078,781, U.S. Pat. No. 5,634,986, U.S. Pat. No. 5,653,970,U.S. Pat. No. 3,337,463, and U.S. Pat. No. 2,979,528, the disclosures ofeach of which are totally incorporated herein by reference. Alsosuitable are ethoxylated 2-naphthol polymers, preferably with amolecular weight of from about 20,000 to about 35,000 and morepreferably from about 25,000 to about 30,000, such as SOLSPERSE 27,000,an ethoxylated 2-naphthol polymer with a molecular weight of 27,000,commercially available from ICI, Wilmington, Del. Mixtures of two ormore polymers can also be employed. The polymer is present in the ink inany desired or effective amount, typically from about 0.01 to about 3percent by weight of the ink, preferably from about 0.05 to about 2percent by weight of the ink, and more preferably from about 0.05 toabout 0.5 percent by weight of the ink, although the amount can beoutside these ranges.

In embodiments of the present invention wherein the ink contains one ofthe above polymers, preferably the ink compositions of the presentinvention also contain an additive selected from the group consisting of(i) diethylene glycol; (ii) glycerol; (iii) trimethylol propane; (iv)urea; (v) n-methyl pyrrolidone; (vi) sulfolane; (vii) 1,4diazabicyclo(2.2.2)octane; (viii) cyclohexylpyrrolidone; and (ix)mixtures thereof. This additive is present in the ink in any desired oreffective amount, typically from about 1 to about 25 percent by weightof the ink, preferably from about 3 to about 20 percent by weight of theink, and more preferably from about 4 to about 15 percent by weight ofthe ink, although the amount can be outside these ranges.

While not being limited to any particular theory, it is believed thatthe polymers in the inks of the present invention inhibit liposomes andemulsified particles formed by the fluorinated material fromflocculating, thereby inhibiting coalescence and shelf destabilization.It is further believed that the stabilization mechanism entails anassociation of the hydrophilic polymer portion with the liposomeexterior surface, while the hydrophobic polymer portion points away fromthe liposome to provide steric hindrance to the approach of anotherliposome, thus inhibiting flocculation. The particular additive oradditives selected, such as diethylene glycol, glycerol, trimethylolpropane, urea, n-methyl pyrrolidone, sulfolane, 1,4diazabicyclo(2.2.2)octane, or cyclohexylpyrrolidone, further enable thisstabilization mechanism. Specific additives tend to be preferred forspecific polymers. For example, inks containing the TETRONIC 904 polymerpreferably contain diethylene glycol, trimethylol propane, urea, orglycerol, and preferably do not contain N-methylpyrrolidinone orsulfolane. Inks containing the TETRONIC 704 polymer preferably containdiethylene glycol, trimethylol propane, N-methylpyrrolidinone,sulfolane, or glycerol, and preferably do not contain urea or 1,4diazabicyclo(2.2.2)octane. Inks containing the PLURONIC 10R-5 polymerpreferably contain diethylene glycol, n-methylpyrrolidone, urea, orglycerol, and preferably do not contain sulfolane or trimethylolpropane. Inks containing the PLURONIC L35 polymer preferably containdiethylene glycol, trimethylol propane, N-methylpyrrolidone, urea, orglycerol, and preferably do not contain sulfolane or tripropylene glycolmonomethyl ether. Inks containing the PLURONIC L64 polymer preferablycontain diethylene glycol, trimethylol propane, N-methylpyrrolidone,urea, or glycerol, and preferably do not contain 1,4 diazabicyclo(2.2.2)octane or tripropylene glycol monomethyl ether. Inks containing thePLURONIC L62F polymer preferably contain diethylene glycol, trimethylolpropane, sulfolane, or urea, and preferably do not containN-methylpyrrolidone or glycerol. Inks containing the TETRONIC 304polymer preferably contain diethylene glycol, trimethylol propane,N-methylpyrrolidone, urea, or glycerol, and preferably do not contain1,4 diazabicyclo(2.2.2)octane or tripropylene glycol monomethyl ether.Inks containing the PLURONIC P65 polymer preferably contain diethyleneglycol, N-methylpyrrolidone, sulfolane, or glycerol, and preferably donot contain urea or trimethylol propane. Inks containing the SOLSPERSE27,000 polymer preferably contain 1,4 diazabicyclo(2.2.2)octane or urea.

Other optional additives to the inks include biocides such as Dowicil150, 200, and 75, benzoate salts, sorbate salts, and the like, presentin an amount of from about 0.0001 to about 4 percent by weight, andpreferably from about 0.01 to about 2.0 percent by weight, pHcontrolling agents such as acids or, bases, phosphate salts,carboxylates salts, sulfite salts, amine salts, and the like, present inan amount of from 0 to about 1 percent by weight and preferably fromabout 0.01 to about 1 percent by weight, or the like.

The ink compositions are generally of a viscosity suitable for use inthermal ink jet printing processes. At room temperature (i.e., about 25°C.), typically, the ink viscosity is no more than about 5 centipoise,and preferably is from about 1 to about 3.5 centipoise, although theviscosity can be outside this range.

Ink compositions of the present invention can be of any suitable ordesired pH. For some embodiments, such as thermal ink jet printingprocesses, typical pH values are from about 8 to about 9.5, preferablyfrom about 8.0 to about 9.0, and more preferably from about 8.5 to about9.0, although the pH can be outside of these ranges.

Ink compositions suitable for ink jet printing can be prepared by anysuitable process. Typically, the inks are prepared by simple mixing ofthe ingredients. One process entails mixing all of the ink ingredientstogether and filtering the mixture to obtain an ink. Inks can beprepared by preparing a conventional ink composition according to anydesired process, such as by mixing the ingredients and filtering,followed by adding any desired additional additives to the mixture andmixing at room temperature with moderate shaking until a homogeneousmixture is obtained, typically from about 5 to about 10 minutes.Alternatively, the optional ink additives can be mixed with the otherink ingredients during the ink preparation process, which takes placeaccording to any desired procedure, such as by mixing all theingredients and filtering.

In one specific embodiment, the ink is subjected to ultrasonification toreduce the particle size of the liposomes in the ink formed by thefluorocarbon material. In this embodiment, the ink is subjected toultrasonication at relatively low intensity, typically for from about 5to about 90 minutes, preferably from about 10 to about 60 minutes, andin a preferred embodiment for about 20 minutes. In another specificembodiment of the present invention, the fluorocarbon material issubjected to ultrasonification prior to admixing it with the other inkingredients. In this second embodiment, the fluorocarbon can beultrasonicated either in the form in which it is received from thesupplier (assuming said form is a liquid containing the fluorocarbon) orafter admixing it with water, mixtures of water and one or more otherdesired ink components, or the like. In a particularly preferredembodiment, the ultrasonicated liquid contains the fluorocarbon materialin an amount of about 15 percent by weight and water in an amount ofabout 85 percent by weight. In another particularly preferredembodiment, the ultrasonicated liquid contains the fluorocarbon materialin an amount of about 15 percent by weight,1,4-diazabicyclo(2.2.2)octane in an amount of about 20 percent byweight, and water in an amount of about 65 percent by weight. In anotherparticularly preferred embodiment, the ultrasonicated liquid containsthe fluorocarbon material in an amount of from about 9 to about 10percent by weight, 1,4-diazabicyclo(2.2.2)octane in an amount of fromabout 6 to about 7 percent by weight, a bisquaternary compound, such ashexamethonium bromide, in an amount of from about 4 to about 5 percentby weight, an acid, such as citric acid, in an amount of from about 2 toabout 3 percent by weight, and the balance water.

One specific example of an ultrasonication process is as follows: LODYNEP-502, obtained from Tricon Colors as an aqueous solution containingabout 15 percent by weight of the fluorocarbon, is divided into 25 gramportions. In each instance, a 25 gram portion of the LODYNE P-502 isplaced in a 30 gram vial. The vial is placed into a 550 SONICDISMEMBRATOR (obtained from Fisher Scientific Co.) tuned at 20 kiloHertzand the LODYNE P-502 is subjected to ultrasonification for a period of10 minutes at an amplitude setting of 5, with the power turned on andoff every 30 seconds. Thereafter the vial is allowed to stand overnight,after which the top layer in the vial is used to prepare inkcompositions.

To avoid excessive heating of the ink during the ultrasonificationprocess, the ink can be jacket cooled during the process, and/or theultrasonification can be pulsed instead of continuous; for example, fora process entailing application of ultrasonification for 5 minutes, theprocess can be pulsed at one second on and one second off alternatelyfor a period of 10 minutes. Reduction in liposome size byultrasonification enables advantages such as enhanced shelf life of theink and reduced ink viscosity. Ultrasonification also results in anarrower range of liposome particle diameters.

In yet another specific embodiment, neither the fluorocarbon nor the inkis subjected to ultrasonification during the formulation process. Inkssuitable for ink jet printing exhibiting a liquid crystalline phase atcertain temperatures are known, as disclosed in, for example, U.S. Pat.No. 5,492,559, U.S. Pat. No. 5,551,973, and U.S. Pat. No. 5,643,357, thedisclosures of each of which are totally incorporated herein byreference. Fluorocarbon materials such as LODYNE P-502, available fromCiba-Geigy, when received from the manufacturer, contain liquid crystalsas observed by microscopic inspection under polarized illumination. Inkscontaining the fluorocarbon and other ink vehicle ingredients, such asbetaine/dipropylene glycol and betaine/imidazole, retain thefluorocarbon liquid crystal structures. When two or more of these inksof different colors are incorporated into a thermal ink jet printer,such as a Hewlett-Packard DeskJet® 500C, and printed onto a substratesuch as plain paper, the resulting multicolored images exhibit improvedintercolor bleed repression characteristics compared to inks ofidentical composition but wherein the fluorocarbon was ultrasonifiedprior to incorporation into the ink composition and inks of identicalcomposition which were subjected to ultrasonification subsequent to inkpreparation.

The present invention is also directed to a process which entailsincorporating an ink composition of the present invention into an inkjet printing apparatus and causing droplets of the ink composition to beejected in an imagewise pattern onto a substrate. In a particularlypreferred embodiment, the printing apparatus employs a thermal ink jetprocess wherein the ink in the nozzles is selectively heated in animagewise pattern, thereby causing droplets of the ink to be ejected inimagewise pattern. Any suitable substrate can be employed, includingplain papers such as Xerox® 4024 papers, ruled notebook paper, bondpaper, silica coated papers such as Sharp Company silica coated paper,JuJo paper, and the like, transparency materials, fabrics, textileproducts, plastics, polymeric films, inorganic substrates such as metalsand wood, and the like. In a preferred embodiment, the process entailsprinting onto a porous or ink absorbent substrate, such as plain paper.

Specific embodiments of the invention will now be described in detail.These examples are intended to be illustrative, and the invention is notlimited to the materials, conditions, or process parameters set forth inthese embodiments. All parts and percentages are by weight unlessotherwise indicated.

EXAMPLE I

To 59.4 grams of distilled water was added 19.8 grams of1,4-diazabicyclo(2.2.2)octane (obtained from Aldrich Chemical Co.,Milwaukee, Wis., D2,780-2), 7.8 grams of citric acid (obtained fromAldrich Chemical Co., C8,315-5), 13.2 grams of hexamethonium bromidehydrate (obtained from Aldrich Chemical Co., 21,967-3), and 199.8 gramsof LODYNE P-502 (containing 14.9 percent by weight of the fluorinatedmaterial, obtained from Ciba-Geigy, Ardsley, N.Y. (Greensboro, N.C.)).The mixture was stirred for 15 minutes, after which time it exhibited aviscosity of 6.10 centipoise at 250° C. Thereafter, a 25 gram portion ofthe mixture was placed in a 30 gram vial. The vial was placed into a 550SONIC DISMEMBRATOR (obtained from Fisher Scientific Co.) tuned at 20kiloHertz and the LODYNE P-502 was subjected to ultrasonification for aperiod of 60 minutes at an amplitude setting of 5, with the power turnedon and off every 30 seconds. The resulting colorless mixture had aviscosity of 3.57 centipoise at 25° C., a pH of 9.16 at 25° C., aconductivity of 7.62 millimhos, and a surface tension of 28.9 dynes percentimeter.

EXAMPLE II

An ink composition was prepared as follows. To 46.4 grams of deionizedwater were added 0.167 gram of DOWICIL 150/200 biocide (obtained fromDow Chemical Co., Midland, Mich.), 0.0833 gram of polyethylene oxide(bisphenol-A derivative, of the formula ##STR11## molecular weight18,500, obtained from Polysciences Corp.), 20.00 grams oftripropyleneglycol monomethylether (DOWANOL TPM, obtained from DowChemical Co.), 41.67 grams of PROJET MAGENTA 1T dye solution (dyesolution contained 10 percent by weight dye solids, obtained from ZenecaColors, Dighton, Mass.), 8.33 grams of Acid Red 52 dye solution (dyesolution contained 10 percent by weight dye solids, obtained from TriconColors, Elmwood Park, N.J.), and an additional 9.90 grams of deionizedwater. The mixture thus prepared was then sonified by the processdescribed in Example I. To the mixture were then added 3.30 grams of1,4-diazabicyclo(2.2.2)octane (obtained from Aldrich Chemical Co.,D2,780-2, Milwaukee, Wis.), 1.3 grams of citric acid (obtained fromAldrich Chemical Co.), 2.2 grams of hexamethonium bromide hydrate(obtained from Aldrich Chemical Co., 21,967-3), and 33.3 grams of LODYNEP-502 (solution containing 14.9 percent by weight fluorocarbon material,obtained from Ciba-Geigy, Ardsley, N.Y. (Greensboro, N.C.)). Theresulting magenta ink composition was then filtered through a 1.2 micron47 mm Gelman filter at 10 pounds per square inch over a period of 55seconds. The ink composition thus prepared exhibited a viscosity of 4.34centipoise at 25° C., a pH of 8.56 at 25° C., a conductivity of 8.46millimhos, and a surface tension of 24.6 dynes per centimeter.

The ink composition thus prepared was then incorporated into aHewlett-Packard 1600C thermal ink jet printer and printed onto Xerox®4024 DP paper and Xerox® Image Series Elite paper. The prints thusformed exhibited low intercolor bleed with a MFLEN value of 5.

EXAMPLE III

An ink composition was prepared as described in Example II except thatthe initial amount of deionized water was 38.1 grams (and not 46.4grams) and that 58.33 grams of PROJET CYAN 1 dye solution (dye solutioncontained 10 percent by weight dye solids, obtained from Zeneca Colors,Dighton, Mass.) was substituted for the PROJET MAGENTA 1T and Acid Red52 dyes. The resulting cyan ink composition was then filtered through a1.2 micron 47 mm Gelman filter at 10 pounds per square inch over aperiod of 65 seconds. The ink composition thus prepared exhibited aviscosity of 3.72 centipoise at 25° C., a pH of 8.79 at 25° C., aconductivity of 7.07 millimhos, and a surface tension of 18.8 dynes percentimeter.

The ink composition thus prepared was then incorporated into aHewlett-Packard 1600C thermal ink jet printer and printed onto Xerox®4024 DP paper and Xerox® Image Series Elite paper. The prints thusformed exhibited low intercolor bleed with a MFLEN value of 5.

EXAMPLE IV

An ink composition was prepared as described in Example II except thatthe initial amount of deionized water was 38.1 grams (and not 46.4grams) and that 33.3 grams of PROJET YELLOW 1G dye solution (dyesolution contained 7.5 percent by weight dye solids, obtained fromZeneca Colors, Dighton, Mass.) and 25.0 grams of Acid Yellow 17 dye (dyesolution contained 10 percent by weight dye solids, obtained from TriconColors, Elmwood Park, N.J.) were substituted for the PROJET MAGENTA 1Tand Acid Red 52 dyes. The resulting cyan ink composition was thenfiltered through a 1.2 micron 47 mm Gelman filter at 10 pounds persquare inch over a period of 50 seconds. The ink composition thusprepared exhibited a viscosity of 4.46 centipoise at 25° C., a pH of8.62 at 25° C., a conductivity of 7.81 millimhos, and a surface tensionof 20 dynes per centimeter.

The ink composition thus prepared was then incorporated into aHewlett-Packard 1600C thermal ink jet printer and printed onto Xerox®4024 DP paper and Xerox® Image Series Elite paper. The prints thusformed exhibited low intercolor bleed with a MFLEN value of 5.

EXAMPLE V

An ink composition was prepared by admixing the following ingredients:

    ______________________________________                                        Ingredient   Supplier      Amount (grams)                                     ______________________________________                                        deionized water                                                                            --            21.81                                              Acid Red 52 dye                                                                            Tricon Colors 15                                                 DOWICIL 150/200                                                                            Dow Chemical Co.                                                                            0.06                                               polyethylene Polysciences  0.03                                               oxide***                                                                      tripropyleneglycol                                                                         Dow Chemical Co.                                                                            6                                                  monomethylether                                                               (DOWANPOL TPM)                                                                N,N'-        Aldrich Chemical Co.                                                                        2.1                                                hexamethylene                                                                 bis(tributyl                                                                  ammonium                                                                      hydroxide)*                                                                   phosphorous acid                                                                           Rhone Poulenc 0.99                                               pH = 8.0 @ 25° C.                                                      LODYNE P-502**                                                                             Ciba-Geigy    12                                                 deionized water                                                                            --            2.01                                               roll mill 30 minutes                                                          ______________________________________                                         *supplied as an aqueous solution containing 20 percent by weight              N,Nhexamethylenebis(tributyl ammonium hydroxide)                              **supplied as a solution containing 14.9 percent by weight fluorocarbon;      sonified prior to use for 1 hour with stirring at a setting of 5 at           45° C.                                                                 ***bisphenolA derivative, molecular weight 18,500, of the formula             ##STR12##                                                                    -  The ink composition thus prepared exhibited a viscosity of 2.97             centipoise at 25° C., a pH of 8.99 at 25.2° C., a surface        tension of 23.8 dynes per centimeter, and a conductivity of 2.82               millimhos.                                                                

The ink composition thus prepared was then incorporated into aHewlett-Packard 1600C thermal ink jet printer and printed onto Xerox®4024 DP paper and Xerox® Image Series Elite paper. The prints thusformed exhibited low intercolor bleed with a MFLEN value of 5.

EXAMPLE VI

An ink composition was prepared by admixing the following ingredients:

    ______________________________________                                        Ingredient  Supplier      Amount (grams)                                      ______________________________________                                        deionized water                                                                             --          44.9                                                betaine     FinnSugar Bioproducts                                                                       15                                                  DOWICIL 150/200                                                                           Dow Chemical Co.                                                                            0.1                                                 butyl carbitol                                                                            Van Waters & Rogers                                                                         2                                                   Reactive Red 180                                                                          Hoechst       3                                                   dye                                                                           Acid Red 52 dye                                                                           Tricon Colors 5                                                   deionized water                                                                             --          5.94                                                sonicate 1 hour with stirring;                                                setting = 5; allowed to heat                                                  to 45° C.                                                              1,4-diazabicyclo(2.                                                                       Aldrich Chemical Co.                                                                        1.98                                                2.2)octane                                                                    citric acid Aldrich Chemical Co.                                                                        0.78                                                hexamethonium                                                                             Aldrich Chemical Co.                                                                        1.32                                                bromide hydrate                                                               LODYNE P-502*                                                                             Ciba-Geigy    19.98                                               ______________________________________                                         *supplied as a solution containing 14.9 percent by weight fluorocarbon;       sonified prior to use for hour with stirring at a setting of 5 at             45° C.                                                            

The resulting ink composition was then filtered through a 1.2 micron 47mm Gelman filter at 10 pounds per square inch. The ink composition thusprepared exhibited a viscosity of 2.49 centipoise at 25° C., a pH of9.02 at 25° C., and a surface tension of 27.1 dynes per centimeter.

The ink composition thus prepared was then incorporated into aHewlett-Packard 1600C thermal ink jet printer and printed onto Xerox®4024 DP paper and Xerox® Image Series Elite paper. The prints thusformed exhibited low intercolor bleed with a MFLEN value of 5.

EXAMPLE VII

An ink composition was prepared by admixing the following ingredients:

    ______________________________________                                        Ingredient   Supplier      Amount (grams)                                     ______________________________________                                        deionized water                                                                            --            53.85                                              polyethylene Polysciences  0.05                                               oxide**                                                                       DOWICIL 150/200                                                                            Dow Chemical Co.                                                                            0.1                                                tripropyleneglycol                                                                         Dow Chemical Co.                                                                            8                                                  monomethylether                                                               (DOWANOL TPM)                                                                 Reactive Red 180                                                                           Hoechst       3                                                  dye                                                                           Acid Red 52 dye                                                                            Tricon Colors 5                                                  deionized water                                                                            --            5.94                                               sonicate 1 hour with stirring;                                                setting = 5; allowed to heat                                                  to 45° C.                                                              1,4-diazabicyclo(2.                                                                        Aldrich Chemical Co.                                                                        1.98                                               2.2)octane                                                                    citric acid  Aldrich Chemical Co.                                                                        0.78                                               hexamethonium                                                                              Aldrich Chemical Co.                                                                        1.32                                               bromide hydrate                                                               LODYNE P-502*                                                                              Ciba-Geigy    19.98                                              ______________________________________                                         *supplied as a solution containing 14.9 percent by weight fluorocarbon        **bisphenolA derivative, molecular weight 18,500, of the formula              ##STR13##                                                                    -  The resulting ink composition was then filtered through a 1.2 micron 47     mm Gelman filter at 10 pounds per square inch. The ink composition thus        prepared exhibited a viscosity of 2.15 centipoise at 25° C., a pH       of 8.80 at 25° C., and a surface tension of 26.8 dynes per              centimeter.                                                               

The ink composition thus prepared was then incorporated into aHewlett-Packard 1600C thermal ink jet printer and printed onto Xerox®4024 DP paper and Xerox® Image Series Elite paper. The prints thusformed exhibited low intercolor bleed with a MFLEN value of 5.

Other embodiments and modifications of the present invention may occurto those of ordinary skill in the art subsequent to a review of theinformation presented herein; these embodiments and modifications, aswell as equivalents thereof, are also included within the scope of thisinvention.

What is claimed is:
 1. An ink composition which comprises water, a dyeselected from the group consisting of Direct Blue 199, Direct Yellow132, Acid Yellow 17, Reactive Red 180, Acid Red 52, and mixturesthereof, and a material of the formula (F₃ C(F₂ C)_(n) CH═CHCH₂OCH(OH)CH₂)₂ NCH₂ COO⁻ ! X⁺ !, wherein X is a cation and n is an integerof from about 3 to about 20, wherein the ink is substantially free ofimidazole.
 2. An ink composition according to claim 1 wherein thematerial of the formula (F₃ C(F₂ C)_(n) CH═CHCH₂ OCH(OH)CH₂)₂ NCH₂ COO⁻! X⁺ ! is present in an amount of from about 0.1 to about 10 percent byweight of the ink.
 3. An ink composition according to claim 1 wherein Xis selected from the group consisting of (HO--CH₂ CH₂)₂ NH₂ ⁺, (HO--CH₂CH₂)₃ NH⁺, tris(hydroxymethyl)aminomethane hydrochloride,tris(hydroxymethyl)aminomethane hydrocitrate, protonated1,4-diazabicyclo(2.2.2)octane, and mixtures thereof.
 4. An inkcomposition according to claim 1 wherein the dye is present in an amountof from about 0.5 to about 15 percent by weight of the ink.
 5. An inkcomposition according to claim 1 wherein the dye is present in an amountof from about 1 to about 6 percent by weight of the ink.
 6. An inkcomposition according to claim 1 wherein the dye is a mixture ofReactive Red 180 and Acid Red
 52. 7. An ink composition according toclaim 1 wherein the dye is Direct Blue
 199. 8. An ink compositionaccording to claim 1 wherein the dye is a mixture of Direct Yellow 132and Acid Yellow
 17. 9. An ink composition according to claim 1 furthercontaining tripropylene glycol monomethyl ether.
 10. A process whichcomprises (i) incorporating into an ink jet printing apparatus an inkcomposition comprising water, a dye selected from the group consistingof Direct Blue 199, Direct Yellow 132, Acid Yellow 17, Reactive Red 180,Acid Red 52, and mixtures thereof, and a material of the formula (F₃C(F₂ C)_(n) CH═CHCH₂ OCH(OH)CH₂)₂ NCH₂ COO⁻ ! X⁺ !, wherein X is acation and n is an integer of from about 3 to about 20, wherein the inkis substantially free of imidazole; and (ii) causing droplets of the inkcomposition to be ejected in an imagewise pattern onto a substrate. 11.A process according to claim 10 wherein the printing apparatus employs athermal ink jet process wherein the ink in the nozzles is selectivelyheated in an imagewise pattern, thereby causing droplets of the ink tobe ejected in imagewise pattern.